Check the picture below.
well, ahemmm if that's the case, namely that AB ⟂ EB that means that the ∡ABE is 90 degrees, notice in the picture that the flat-line of ABC is 180 degrees, all flat-lines are anyway, now, if DB ⟂ BF, that also means that ∡DBF is also 90 degrees.
If we subtract from 180, 90, what we're left with is 180 - 90 = 90, namely if we subtract the pink angle from the 180 one, what we're left with is 90, the green angles.
We know that ∡CBE is 90, so whatever ∡EBF is, must the the complementary of ∡CBF, and since both green angles are complementary, then it must be that ∡EBF = ∡ABD, because ∡ABD is also complementary of ∡CBF.
